Rambling on Software

Mostly about software, but I can ramble about anything...

I read through a lot of Microsoft's material on Volta the other day. I sense the turning of the karmic wheel of software development. They note on their blog that Volta "enables developers to postpone architectural decisions about distribution." Well, having spent 3 or 4 years deeply involved with building infrastructures on top of CORBA, I can safely assert that this is exactly one of the goals that we had in building those infrastructures, and I think it is safe to say that it was one of the primary goals behind CORBA itself. In fact, the whole point of location transparency was just that: to completely isolate code from decisions about where objects actually reside. Oddly, the Volta folks point out that they acknowledge the failure of location transparency by referring to the fallacies of distributed computing. But location transparency is not really one of those fallacies; the fallacies are about more fundamental issues in distributed computing such as the fact that latency is not zero and cannot be ignored.

One of the biggest problems with location transparency is that people misinterpreted it as meaning that location could be ignored. But anyone who was seriously involved in research in distributed computing -- including the folks who designed the CORBA specs, knew that was not the case. Location transparency was about creating systems in which the syntax and semantics of invocation were the same regardless of where an object was located. And the primary reason why location transparency was a goal in CORBA was precisely because it allowed the physical mapping of objects to servers to be changed without having to change code. Sounds oddly like allowing "developers [to] architect their applications as a single-tier application, then make decisions about moving logic to other tiers late in the development process" -- which is straight from the Volta FAQ.

Part of the downfall of CORBA was that location transparency allowed people to build systems badly. In fact, I think it would be safe to say that unless you were thinking very carefully about patterns of object interaction, the physical locations of objects, the types of partial failures possible, etc. you were pretty much guaranteed failure. The Volta folks seem to be treading in similar territory. Unless they have mechanisms in place to prevent people from building poorly architected systems, then people will build poorly architected systems. And it will only be too easy to have the technology be the scapegoat.